The 210 [B310] used the H150 differential, as did most of the b210 models.
The most common ratio was 3.9 to 1, but 3.54 to 1 was not uncommon. I am surprised that you are unable to come up with a replacement as differentials are not the biggest selling item in wrecking yards.

If you examine the manufacturers build plates in the engine bay you should be able to determine the original ratio, & I think that you should have less difficulty finding a replacement differential than finding & fitting a complete rear end from an A10 car.