To use FindMy from a browser, go to https://icloud.com/find
Including the “/find” allows you to search for your phone w/o needing the 2FA Verification Code.
See:
If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support
CRITICAL:
Expect messages from the theives masquerading as Apple (or the police) claiming to have found your phone and “needing” your AppleID credentials.
These messages - while appearing VERY convincing - are NOT from Apple or any legitimate entity; they ARE from the criminals phishing for your info to re-use your phone and/or takeover your AppleID.
NEVER respond to these messages or follow any links which they might contain.
LASTLY:
NEVER perform “Step 7” in the Apple article; doing so allows the thieves to re-use your phone after they’ve erased it.