Un archive mailbox

Hello Friends,

My organization is planning to move my on premise exchange mailboxes to office 365 .

For this we have to move the data in archive mailbox  for all users back to Main mailbox.

I use exchange native archiving. Is it possible. How can I do it.

We have only 50 mailboxes. and on exchange server 2013.

Please help.

Thanks

Roopesh Raj