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Can I say,

(a) He put all the jewellery into a pack of sack to the robber.
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Hi,

Can I say,

(a) He put all the jewellery into a pack of sack to the robber.

No. Say 'into a sack'. Or perhaps 'into a back pack' or 'into a bag'. 'A bag' is commonly said in such contexts.

Clive
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(a) He put all the jewellery into a bag that he gave to the robber.