Make a 4×4 grid

Read down from the upper right M

mjj83darkxm959rx

After trying rectangles, morse and a few other cipher, a skip of 2 gave this

ujh34689rvb0117zvzby

You can see the prefix and suffix at the start of the string, let’s split it

ujh34689rv

b0117zvzby

Searching the second string on google gives a reference to the book The Niantic Project: Ingress by Felicia Hajra Lee

A few option for keywords but hajra gets the valid passcode

ujh34hajra689rv

That / gives it away for a keyboard mirror cipher. 1=0, q=p a=; and z=/

zvr42587ww

Now for the keyword, the mirror of / is \ which is glyph for destroy

zvr42destroy587ww