The Shrine of Mool Ah in Tiny Tina’s Wonderlands is located in the Overworld near the beginning of the area.
The shrine pieces for the Shrine of Mool Ah can be found below. Once you collect both of them, return to the shrine to hand them over thus completing the challenge.
Shrine Piece 1
To obtain this piece, complete the Knife to Meet You side quest.
Shrine Piece 2
When facing the shrine, head to the encounter on your left.
Clear the area to proceed forward. When you emerge from the encounter, grab the shrine piece!