I know its expensive, but get a stool sample analysed before you worm. There are different (sheep) wormers out there, and your vet should avise on which one to use (depends on what worms there are), some are by injection (Ivermectins) and others by mouth (Panacur, or white drenches)). Goat dose is about 1.5 times sheep dose if I remember correctly. But if their stools are clear, don't worm, otheriwse they will just become resistant (the worms that is).
There are lots of people out there who don't worm ever, if your land did not have sheep or goats on it for more than a year and you wormed your goats on arrival (or even better on leaving their previous holding), then you should keep them in for a few days anyway, and they should be worm free on coming onto clean pasture. If no movements on/off take place, no sheep etc come in - no worms!
Only one to watch our for is fluke if your pasture is wet. But can be done with the same stool sample at the same time as normal worm count.