Please return the valuables I left with you.

Literal

Deposit-had [attributive-の] valuables [object-を] return-please.

預ける ('entrust / deposit [something to someone]') is transitive. 預けていた is past ongoing — 'the state of having deposited.' 貴重品 ('valuables'). 返却する is the formal 'return / give back' (more formal than 返す).