Oh, I hope you haven’t had an interrogation already. The kind of lawyer you need depends on what kind of investigation you are under.
You want the kind of lawyer who handles federal offenses of whatever it is you are being questioned about or believe you will be questioned about. Start by searching online for some of the terms the FBI used for its interrogation, assuming you have already been interrogated. For example, if you are being questioned about hacking, you want to look for a lawyer who specifically has experience representing hackers. If you have been told you will be interrogated but have not yet been, please get a lawyer before you meet with the FBI.