You've received some good advice but I'll give a bit more.
After you pull it apart get a rag or paper towels and wipe the grease out of the hub and off the bearings. Now inspect the bearings for wear, my guess is they will be fine unless the axles were submerged in water for a while.
All bearings will have a number stamped on them that you can use to buy new ones if needed.
replace bearings as a pair. (both outer and inner at the same time)
Replace the races with the bearings, They wear together, do not replace only half of a set.
Most grease seals do not have an identification number on them. A decent trailer supply store can measure the seals with a caliper and sell replacements.
When finished document all the part numbers used for the future.