Not same model but one of mine has zerk facing rear in center of axle and the other machine has two, one front one rear.
See if Kubota parts diagrams online can provide help finding. IF can find it by part number may desire---if you want a known 'right' part---to order a couple from dealer by part number in order to have 'samples' for that particular zerk to go hunting at local auto parts house. Or compare part numbrs for other locations on machine and pull one to go parts-a-hunting.
Also consider that zerk may be unscrewed missing or twisted / broken / sheared off. If replacing, consider the thread may be metric (some are, some aren't; some places on same machine are different especially FELs / backhoes). If you can't gauge threads try several by hand until something 'feels' right before applying wrench. Or follow as above to get samples in hand during buying expedition. Good luck.
Last, don't be tempted to use a hammer-in type zerk. Stay with threaded.