You can write to Malik at:
Malik Muhammad #23935744
Oregon State Penitentiary
2605 State Street
Salem, OR 97310
Malik can also receive communications electronically, and prefers that method for consistent correspondence. You can find instructions for setting up electronic messages via the GettingOut website here:
https://www.icscorrections.com/docs/Gettingout_instructions.pdf
*Note that you must first send your email address to Malik in writing so that he can add you to his list of approved contacts.