How to identify V-in V-out pins on Lineage Regulator?
Some assumptions: You likely have a higher voltage input to the board, and a lower voltage to that other IC on the board.

Find continuity between one of those regulator pins and where ever power comes into the PCB, and you will have your input pin.

Find continuity between the regulator and any pin from the other IC that is not ground. That should be the output pin.

There is not enough information in the post for a more definitive answer, so this is just the best guess.