Yeah, a device with a pulse output! So you are a lucky guy! This is the perfect connection for a microcontroller, much easier to use than a noisy A/D conversion. Usually these frequency outputs are "open collector" outputs. An NPN transistor is connected to ground with its emitter and its collecter is open. Sometimes there is an option to use a buildin resistor which is pulled-up from that collector to higher voltage(24V?). You can adapt an optocoupler with a matching resistor to keep the 24V away from the arduino. There are fast and slow couplers available but I do not remember their names...
For your next project I would recommend to use a ModBus device. They are connected via cheap RS-485 or ethernet (ModBus TCP) and the protocoll is widely known for more than 40 years. Downside: Back in these days the fight for "the best endian ever" was at its hight. So each device can be configured how a 32bit variable is stored in two 16bit pieces and there was never a standard evolved where these important switches can be read out. But the datasheet will tell you details about this.
I hope you pass all certifications and can continue your work!