what season can I uplift & replant a plum tree

When its dormant which is late autumn to early spring. October is the best time.

thank you for your help

Your welcome read above I added info

You don't say how big the tree is - if its not been in more than couple of years at most, you will probably be able to move it easily, but if its over 10 feet, say, and it's been in years, then you will have great difficulty in transplanting it successfully. Do it when its completely dormant, as Morgana says, and try to dig as big a rootball as you can and keep it intact.

The tree is about 3-4 yrs old & I'm unsure of height.At a guess I would say about 10 feet but that's taken into account the length of some of the branches,they are rather long.
Do we also cut it right back Morgana never said or is October the month for moving & cutting like they replied.

Well its not recommended to cut plums in the winter because of the risk of silver leaf, but I personally doubt you will successfully remove the tree and have it fit to replant anyway, if its been in situ that long and is that big. You could give it a go though, but don't cut it - prune back the flowering branches after you've taken the crop, so any time now, really, and move it when its dormant in the late autumn/winter.

thank you both for your help,much appreciated.