The numbers are estimated at closer to 40 million.
Anyway, you just enforce current laws & they return themselves. One could simply seize part of their illegal assets, say, starting after the first month. Each passing week the percentage would ramp up until 100% or higher. The mass exodus would be
instant.
It's humorous (and tiring) when people spew the Democratic talking points like it's some impossibility.
Trump has shown his thoughts from history on the matter here:
http://www.politifact.com/truth-o-meter/statements/2015/nov/11/donald-trump/trump-eisenhower-deported-15-million-immigrants/