Those look like CRT units without cases, which is slightly terrifying. Be careful.

What’s on the back of it (i.e. connectors) and what country are you in? (i.e. PAL, SECAM, NTSC)

Likely connectors are RF aerial, BNC, component, composite. Maybe s-video?

Assuming they still work and power on safely, you may find the issue is in generating a signal that they accept, with modern equipment. This depends a little on what you’re planning on using them for, and therefore what you want to connect them to.