The 19-year-old is yet to make his first-team debut for his Brazilian club but has been linked with a number of European sides over the last few months.
Barca are believed to have already paid an initial €1m (£890,000) to secure first option on the attacker, although they have to commit to paying another €3.5m (£3.1m) to sign him before the end of June.
Silva is confident that the Spanish champions "will complete the purchase" in the coming weeks.
"We're sure that Barcelona will complete the purchase," Silva told Radio Transamerica. "There has already been a signal from [Barcelona] and Maia has already started Spanish classes to prepare himself more.
"Other clubs were interested in the last few months, but he never had any doubts: he always wanted to go to Barcelona."