Given that your two flights will be on separate tickets/bookings.
In that case:
You need to:
Deplane (can take a good 15 minutes if you are at the back of a 777 or 380).
Get to immigration. Dubai airport is large, and some gates require you to take an inter-concourse people mover. I'd count a good 15 minutes for that.
Go though immigration. No idea what ...