I have upgrade my rotary tool to a Forefom micromotor, I now have the issue of none of my current burrs etc fit as they all have a 3mm shank rather than the 2.35mm which is required for the foredom micromotor. I’m trying to find online some sort of reducer collet but not sure which is best, can anyone who has had this problem previously advise me on this please? TIA

They should have the kit where you bought the micro motor.
They should be able to give you hood advice.
Regards Per-Ove

Which micro micromotor did you buy, the foredom portable? If so, it comes with either a 1/8" or 3/32" handpiece. I have the 1/8" model and an adapter to use 3/32" burs.
It sounds like you might have the 3/32" handpiece and have 1/8" (3.175mm) burs?.
As I understand it, I don’t believe that they make a 3/32 to 1/8 adapter, which is why it was recommended to buy the 1/8" model. Perhaps you can swap it out?

If that is not an option, I think you can buy the 1/8" collet (not adapter) from foredom to convert your handpiece.

If/when you do get the 1/8" handpiece, one thing to note about the 1/8" collet and 3/32" burs: Rio sells a 3mm to 3/32" adapter but this is not what is necessary to use 3/32" burs. That 3mm adapter will be quite loose inside the 1/8" collet and falls out very easily when changing burs. I lost mine on the first day. Rio doesn’t seem to understand the difference between 3mm and 1/8". What you need is this foredom part:
Collet Adapters - HPL4-3236 – 1/8″ – 3/32″
Rio does not carry this and it must be purchased separately from foredom.