This ipad 3 my boss was give they for get ID I want use how can I rese

Only feasible and economical way to remove their old ID is to reset the password and sign out. Any "backdoor" solution may be expensive or only temporary in a sense. Some services can bypass it but if the device needs to be restored for whatever reason, it'll become locked to your boss's ID again. If you can't get rid of their old ID, it would be best just to seek out another device. The mini 3 hasn't received updates in a few years so the only thing it would be good for is web browsing, facetime/imessage, or music/movies. Really wouldn't be able to install any apps or would have a very limited number of apps you could install.