Out of curiosity, did you host your server as a public one that is advertised as open to all? Or did you just not set access controls and someone just found it?

You can try this https://www.iwf.org.uk/en/uk-report/

I would suggest doing it with the tor browser as to not be associated with it in any way.

Sadly without the actual content and giving your server away for forensics, this might not go anywhere. But! It can help build a case, especially if any of the pii (ip, username, etc) you provide is already being investigated.