Hi @Akanitz, welcome to the Sonos Community!
They likely are passive speakers, but the best way to tell would be checking how they’re currently (or how they were previously) connected. If they are wired into the back of another device via banana plugs, speaker wire, or similar, then they’re passive. If they have to be plugged directly into a power outlet then they’d be powered speakers.
For passive speakers, you’d need the Sonos Amp. You wont be able to connect all five speakers to the Sonos Amp but we do have a support article for connecting four speakers to the Sonos Amp. Once they are wired, you can then connect the Sonos Amp to your TV via the HDMI port on the back of the Amp to the HDMI ARC/eARC port on the back of your TV.
This will let you play TV audio, albeit in stereo. You’ll need to use a second Sonos Amp to act as the rear channels if you want surround sound which is explained under the ‘Use Amp for home theater’ section of our Sonos Amp setup article.
If you have any other questions then please let me know and I hope this information helps!