As far as I know, there is no airside transfer between Terminal 3 and another terminal (Terminal 3 is the low cost terminal for charter flights and very low cost carriers – even EasyJet does not not use).
You will have to disembark, pass the immigration, collect your luggage, pass the customs, go to the terminal 3 (a little walk + CDGVAL + more walk) and register before the time limit (it depends probably from the airline, but often 1 hour).
Depending on the terminal where you arrive, your nationality and your status, whether you have checked your luggage or not, this can go from very bad to very good if the incoming flight is at the hour. Quickly impossible if there are delays.
In addition, since this connection is almost certainly on two separate tickets, remember that if you do not respect the time limit for check-in and baggage deposit for the second flight, they will consider you as a no-show, will cancel your ticket (and possibly the following flights). on the same ticket, depending on the airline), and you will have the opportunity to book and pay a new ticket (at the last minute, so usually a little more expensive).
If you have not booked yet or if you still have the option to change one or the other flight, I highly recommend booking again with a lot more margin.