The micro sign is on the umlaut panel

The Micro sign µ (or Greek mu) is on the umlaut panel:

An easy way to remember the position (as well as the reason why it is there) is that it is at the place of the letter m (as in mu or micro).

Jean Ichbiah

PS. When in doubt on letters, you can always go to the Character Reference. There you will see the entry for Micro sign.