First the tubes are packed in their own boxes. Each box will have the respective tube socket number written on each of them. Or at least each tested match pair. The owners manual will have a block diagram showing the tube layout. Your amp may even have the socket number stamped be side each of the sockets. This is for a new amp. If you are buying a used amp, hopefully the seller kept the original tube boxes, and as he pulled the tubes out put them back into their respective box. Or at the very least identified them in someway. If they are not identified...contact the seller.
Is this amp new or used? If used there is more you need to know.