When dual wielding, can the character move in between the attack with the main hand and the off hand attack?
Yes, you get to break up your movement and do some before, some after, and even some between attacks.
Quoting the SRD on movement:
Breaking Up Your Move
You can break up your movement on your turn, using some of your speed before and after your action. For example, if you have a speed of 30 feet, you can move 10 feet, take your action, and then move 20 feet.
Moving between Attacks
If you take an action that includes more than one weapon attack, you can break up your movement even further by moving between those attacks. For example, a fighter who can make two attacks with the Extra Attack feature and who has a speed of 25 feet could move 10 feet, make an attack, move 15 feet, and then attack again.