You must supply your own 9VDC 500ma power supply with a 2.1mm x 5.5mm barrel connector (center positive).  I use my bench power supply.  Previous purchasers say the following work with the RCT Pro:

https://www.amazon.com/dp/B082VVSLGR

https://www.parts-express.com/9-VDC-1.1A-AC-Adapter-with-Five-Interchangeable-International-AC-plugs-129-230

For more details about this tester and the extensive ~166 page manual for its use, please see:
https://8bit-museum.de/sonstiges/hardware-projekte/hardware-projekte-chip-tester-english/
https://8bit-museum.de/sonstiges/hardware-projekte/hardware-projekte-chip-tester-firmware/

The tester was reviewed on YouTube by Adrian's Digital Basement:
https://www.youtube.com/watch?v=n46oM3jXmtU
You can see the assembly process and the uses for the tester there.

Firmware updates are fairly frequent. Please send me your e-mail address so I can provide it to Stephan who designed the Retro Chip Tester Pro, if you haven’t already. This will allow you to get firmware updates.

If you aren't willing to upgrade your own firmware, I strongly discourage you from buying the RCT as firmware updates which expand its capabilities are frequent.

In order to update the firmware which is updated frequently, I recommend using a Pololu USB AVR Programmer v2.1 which can be purchased from Pololu.

I keep a few of these on hand as well that you can add to your RCT Pro assembled board purchase at checkout. 

If you want to dump (EP)ROMs, you will need to buy a micro SD card adapter.  They are inexpensive.  

You can get them on eBay or Amazon but I usually have a few on hand as well that you can add to your RCT Pro assembled board purchase for $4 each upon request.