if i have full custody of my child can my fiancé adopt it if so how much does it cost?

My ex gf got prego an it was mine when she had the child i had a dna test done bc she wasnt sure if it was mine i took her to court fpr custody and was granted it i started seeing someone when we broke up because we had a good relationship and have been amazing friends and both know how it feels anyways she is prego with my child and we are engaged im pretty much looking at what are my options. With my first child with my ex could my fiancé adopt her or what im not really sure