Can I use Charm to move an enemy unit at a battlefield to a battlefield I control?

Yes, you can use Charm to move an enemy unit from one battlefield to a battlefield you control.

According to RiftJudge FAQ #7385, you can use Charm to move an enemy unit from anywhere on the board (including from another battlefield) to a battlefield you occupy. This movement is not restricted by standard movement rules (like the Ganking keyword), as Charm is a card effect and not a Standard Move.

Furthermore, if you move the enemy unit to a battlefield you occupy, this will force a showdown, and the opponent who controls the unit you moved will become the attacker in that showdown.