I have my back pack and I would love to know if there is lockers to leave it at the Moma museum

And it's free!

Yes, coat check will hold it for you. It's free.

Coat check will hold it for you during your visit.

Coat check will hold your backpack for the day.

I believe there is a coat check room where you can also leave your backpack.

Not necessarily lockers, but you can drop off your coat and belongings with them

Theres a coat check. They tag backpacks