"Had past run in with F.B.I.
Are there digits / a code I can use
to prevent if my phone is tapped???"
Sorry. Dialing a "special telephone number" to see if a phone is tapped is an urban legend which had a grain of truth before the phone company switched over to electronic switching in the 70's-80's.
Today, legitimate law enforcement wiretaps are not preventable by the target (you). This is because modern taps do not change the electrical characteristics of the phone line.