What should I do if I lost my phone and cannot remember my apple Password to log into find my device?

First, go to https://iforgot.apple.com/ to regain access to your AppleID.

If that fails, follow link in “Related Article” to regain account access.

Then use FindMy to “Mark as Lost” your iPhone.

Finally, follow-up w/ the other steps listed here:

https://support.apple.com/en-us/HT201472