One power supply for Arduino and Motors

I want to run arduino uno and 2 selenoids+1water pump motor with only one power supply.(adapter from the wall outlet)

selenoid - 12V DC / 1A
water pump motor - 5V DC / ~100mA

I am new at this and don't know the electronics well.
How i split the power like 24V 3A adapter(hypothetically) to give arduino and these selenoids+w.pump correct electricity.
I saw the people saying use this and lower the Voltage what u need. But don't we need the calculate the ampere either?
I don't know the which electronic part to use. Just want to give the correct V and A to each of this parts

The voltage should "match" the solenoid & motor requirements, so 12V for the solenoids and 5V for the pump.

The power supply's current rating (Amps) should exceed the requirements so 3A for the two solenoids, plus a little for the Arduino & pump motor is fine. The circuitry will only take as much current as it needs... i.e. If you connect a little LED and the usual current-limiting resistor to a 3A power supply, you'll get the usual 10-20mA out of the power supply (Ohm's Law).

You'll need a different power supply or a step-down voltage regulator (or two).

The Arduino has an on-board 5V regulator and it's rated to work from 7-20V. Or, you can bypass the regulator and power it from 5V.

The pump motor should probably have it's own 5V regulator because 100mA might be "pushing it", and motors & solenoids can make "glitches" on the power supply that might reset the processor. Separate regulators help to "isolate" those glitches.

You'll also need transistor or MOSFET drivers, or relays for the solenoids & pump. The Arduino only puts-out a 5V low-current "signal" and it can't directly "power" anything other than an LED.

You can use one primary power supply (wall wart or battery), and any number of voltage converters (up/down) for the other voltages. I'd chose the primary supply for the most power hungry devices, in your case a 12V DC supply for the solenoid, and one (better 2) step down converter from 12V to 5V for the water pump and Arduino.

Rule of thumb: whenever a transistor is required to turn a device on and off, that device should have a power supply different from the Arduino Vcc.

DVDdoug:
The voltage should "match" the solenoid & motor requirements, so 12V for the solenoids and 5V for the pump.

The power supply's current rating (Amps) should exceed the requirements so 3A for the two solenoids, plus a little for the Arduino & pump motor is fine. The circuitry will only take as much current as it needs... i.e. If you connect a little LED and the usual current-limiting resistor to a 3A power supply, you'll get the usual 10-20mA out of the power supply (Ohm's Law).

You'll need a different power supply or a step-down voltage regulator (or two).

The Arduino has an on-board 5V regulator and it's rated to work from 7-20V. Or, you can bypass the regulator and power it from 5V.

The pump motor should probably have it's own 5V regulator because 100mA might be "pushing it", and motors & solenoids can make "glitches" on the power supply that might reset the processor. Separate regulators help to "isolate" those glitches.

You'll also need transistor or MOSFET drivers, or relays for the solenoids & pump. The Arduino only puts-out a 5V low-current "signal" and it can't directly "power" anything other than an LED.

So i draw something like this but I wonder do i need to add diode for motors or do i need to add resistor?

In case you mean these:

Diodes are required for all inductive loads.

Gate resistors are required with MOSFETs.