Right. That's my bad. I edited the image to remove some stuff that might have been confusing to OP but I didn't notice the line segments left behind. Those can be ignored.
The original post has been edited
The original request was for level changing, 30-volts to 5-volts or something like.
I'm not sure what they want.
The least invasive way is to measure motor current, by cutting the relative motor wires and running them through a current sensor (motor current is more importany than voltage)
You could do that for example with these sensors (they are 3V3 compatible and isolated).
You might need 2-5 of them, depending on how the 6-wire motor is used.
You will then have up to five analogue signals, representing the motor currents.
I have no clue how to interpret them to get step/dir speed from that.
Your best (only) way to monitor/control a stepper motor is to tap into the control inputs of the driver, not the motor wires.
I am not sure OP wants to control the motor, but just monitor it.
I was thinking similar to @Wawa. But instead of cutting wires, is there a way to measure current at the inputs on the driver? And then figure out the math from there, if that math is possible to figure out.
Edit>>no wait, that won't work. Current is measured in series.
The input of the driver works with voltages, so no need to cut wires there, just tap the voltage.
That could be 5volt. An oscilloscope might be needed initially.
Seems like control to me.
I got to thinking about it, measuring current at the inputs wouldn't work because it wouldn't be in series.
touché! I missed that.
Step/dir signals is the industry standard, but unfortunately not the only one.
Op is in deep water without extensive knowledge and a scope.
Maybe op can monitor the stepper with hall sensors (magnet mounted on output shaft) or encoder.
From a distance he might want to control the stepper manually...
This approach will be much safer (no hassle with wires from inductive components). And should work for the monitoring part.
My favorite for receiving high-voltage digital signals is a 74HCT14. A 100 kΩ series resistor from the input voltage to the HCT14 input works well in many applications, and you can add a capacitor to ground if you want to provide debouncing or noise filtering.
This approach relies on the input protection diode inside the 74HCT14, which begins to conduct when the input rises about 0.5–0.7 V above VCC. With a 30 V input and a 100 kΩ resistor, the clamp current is only about 250 µA, well below the typical absolute maximum rating.
One thing to watch for is that the circuit powered from 3.3 V must be able to absorb this small current. Otherwise, the forward-biased protection diode can raise the supply voltage if the regulator or load cannot sink the injected current. It also should not be used if the IC is unpowered while the input voltage is present.
A more conventional approach is to reduce the voltage before it reaches the input. For example, a resistor divider such as 270 kΩ and 47 kΩ will reduce 30 V to about 4.5 V, eliminating the need to rely on the input protection diode.esistor divider (e.g., 270 kΩ and 47 kΩ for about 4.5 V from 30 volts).
@insas
The motor has a controller/driver now with some sort of command capability so why not just use that remotely?
So far we have seen no information or pictures of the driver,
The signals from your motor controller will be noisy anyway and I’ve no idea how you would decode them
If you can put a simple opto pickup on the motor shaft you will get a simple clean rpm signal. Use a current transmitter if you want to measure current .
And what resolution should that pickup be. The stepper could be operating in micro-stepping.
The best way is to record the input signals of the stepper motor.
Hmmm….good point
Really need to know more about this - a shaft encoder might be better . Just recording the motor controller output will probably not give you a reliable absolute position, only up down steps if you can decode and do the sums (?)
What is the project and why do you need this data ? - that info may lead to a better solution
I think it’s a typical X/Y problem. The OP thought he had a solution and just needed a suitable level converter. And that’s all he asked for. He was obviously unaware that he couldn’t actually solve his original problem that way, which is why he didn’t mention it at all. And now he seems to have lost interest in it.
I always love these threads. Someone posts a weird ask then disappears. And the next 40 posts are all about how impossible it is while OP is nowhere to be seen 
The photo shows the step angle .
Steps per revolution = 360 deg/step angle = 360/1.8 = 200 steps per revolution.
You should be able to measure the rpm using millis function if you count the steps. This doesn't require any h/w feedback
Happens a lot.
Something you have to live with.
One of the perils of a free advisory service.