Leicester finished 18th in the Premiership and join in round 2 while Millwall get a bye to the third round for being in Europe.
The 35 first round winners will be joined by 14 Premier League clubs and Leicester City to create 25 second round ties.
The 25 2nd round winners will then be joined in round 3 by the 6 Premiership clubs in European competition and Millwall. Thereby balancing the draw with 32 teams.
The first round is one legged with no replays. A result will be determined on the night.