Can I change my daughters surname to my future husbands surname? Her biological father hasn't been in contact for 6 years but his name is on her birth certificate

No. To change a child's name you have to go to court for a legal name change. Otherwise the name on the birth certificate is the legal name.

Why not wait until after you are married and have your husband adopt.

But do I still need his permission, even though I have no idea to where he lives or contact number? He hasn't wanted anything to do with her I never stopped him seeing her I always gave him the opportunity to see her.

She has my surname not his.

That depends on local laws. You have to, at least, show a good faith attempt to contact him.

The court may accept the fact after you present evidence that you tried to contact him, But the court will require at least a level of attempt to find him to notify them. After that most will require notice be given though publication, but it really varies,