The page about Mentor Intervention Requests can be confusing, and the form can be tricky. Once you are sure you need to file an MIR, you need to:
I assume you have gone through the Problems with Members process?
If you have and you still have a problem, then this is the MIR page
These are the instructions
If Problems with Members procedure directs you to file an MIR, go to the profile of the member with whom you are having the problem. If you're a Project Leader look at the bottom of the profile under the Leader Links. If you're not a Leader, copy the member's WikiTree ID and replace WikiTree-1 in the URL https://www.wikitree.com/contact/mentor/WikiTree-1 with their ID. Paste the URL into your web browser and click "return".
There is NO specific form - just a procedure you have to follow - see above.
Hope this helps.