Unfortunately you cannot. They are grafted onto a rootstock, beyond the average layman.

If you want to be ambitious, try an 'approach graft' next spring once the Victoria is into good growth. Use a vigorous wild plum of some kind for the root stock (prunus cerasifolia is often used) and bend down a new shoot from the Victoria close to a strong shoot on the root stock. Strip the green surface layer from both, and tie them tightly and closely together with insulating tape.
Leave them both growing like this for a couple of months at least, and then you should be able to sever the shoot from the Victoria and it should have made a union with the root stock. Grow on like this to the end of the season when you can carefully remove the tape. Cut off any growth from the rootstock below the graft.
The main difficulty in doing this is physically placing the two shoots in close proximity. If the rootstock is in a pot it can be placed near a suitable shoot on the Victoria, or if you are lucky you may have a branch with shoots that can be bent down to the ground.
I did this successfully with a plum which I was able to take with me in the same season when we moved to France in October of the same year.