You can find out here.
If you mean playing 3 CM's
Its like a mix between defensive and offensive football, which not many teams enjoy. Your width is going to come from your FB's, making you prone to the counter from wide teams. Its more a possession based tactic, being heavy in the centre of midfield, and most teams look to either attack, or defend and hit on the counter, rather than sit with the ball in the middle of the park, waiting for that lucky break.
No mate I mean with a DM,then 3 attacking mid : an AMC ,both AMR and AML as inside forwards and 2 upfront