Look at page 4 of the Microfix User Manual.

http://www.acrelectronics.com/common/plb300man.pdf

It shows the "UIN Label: Applied at the factory, the 15 character hexadecimal number is unique to each beacon." is a whitish horizontal label near the top of the back of the beacon.

The COSPAS-SARSAT label - the one you got from the government when you registered your beacon - is shown placed horizontally directly below the UIN Label.

Hopefully you didn't place the COSPAS-SARSAT label directly over the top of the UIN Label. If you did, then you'll need to peel off the COSPAS-SARSAT label to view the UIN code.

That's not really a big deal. If the sticker doesn't stick well anymore, just go back into the registration database at https://beaconregistration.noaa.gov/rgdb/ and modify it somehow. They'll send you a new updated sticker.