Here's a breakdown:
* हरी मूंग दाल (hari mung daal) - Green gram lentil
* का (ka) - of
* आटा (aata) - flour
So, the full phrase translates to "flour of green gram lentil".
You might also hear it referred to as "मूंग दाल का आटा" (mung daal ka aata), which simply means "mung dal flour".