Using autonumber value as a parameter

I'm trying to query a MS Access database using an autonumber value as the search parameter but I'm getting a

Data type mismatch in criteria expression

error

My code is
sql = "Select * from tblContent where Ad_Id = '" & adID &"'"
Set RS = Conn.Execute(sql)

If anyone can help me I'd really appreciate it.

Thanks

sql = "Select * from tblContent where Ad_Id = '" & adID &"'"
Set RS = Conn.Execute(sql)

just remove the single quote before and after ampersand

following will do
sql = "Select * from tblContent where Ad_Id = " & adID
Set RS = Conn.Execute(sql)