を見つけるのに

to find …

→ を
phrase Rare #30,453
to find … を marks the thing being looked for. This phrase often comes before a result or description of the effort involved in finding it.
JA: 鍵を見つけるのに時間がかかった。
EN: It took a while to find the keys.

やっぱりこの服を見つけるのにすごく苦労したの

I really had a hard time finding these clothes after all.

— 8 1/2 (1963)

バスの停留所を見つけるのに大いに苦労した。

I had a great deal of trouble finding the bus stop.