Hi marshman_67 and welcome to the forum
What you want to do is very easy, if you have all the equipment required.
To copy from DV tape to another DV tape is very easy. All you need is a DV player (another camcorder etc) and a camcorder that has DV-in enabled.
Connect the cams together with a 4 pin to 4 pin firewire cable (about £7 online).
Put them both into VCR mode.
press play on one and record on the other and off you go! easy.
If you have a digital8 cam that can play back Hi8 recordings (or the the recording is D8) then it is exactly the same as for DV.
If the Hi8 is analogue then you will need a pair of phono leads for sound and an S-Video (or composite) lead for video instead of the firewire lead above.
One thing to be aware of though is that your recordings are probably PAL (UK TV system) and therefore the copies will also be PAL. In the USA they use NTSC and therefore may well be unable to play back your PAL tapes. If you do need to send out NTSC tapes then you will need to get them converted proffessionally or buy an expensive PAL>NTSC converter or a PC and editing & conversion software.
Mark