When people say Remember the power of Three , what does it mean?

I m not sure that I understand your question. There are many references to the power of three , but I m not aware of any that pertain to witchcraft.

I am familiar with The Threefold Law. This law is a part of many religions even atheism which is the anti-religion.

In Wicca, it says that whatever you give to the world, you get back three times over. Have you ever used any of these?

An eye for an eye, a tooth for a tooth.

You scratch my back, I’ll scratch yours.

Do unto others as you would have them do unto you.

Schoolyard/playground rules.

They’ll get what they have coming to them.

Reaping what they sow.

Return the favor.

The use of any of these phrases means that you understand the nature of Karma. Its like the golden rule, Do unto others and they will do unto you. In turn, if you’re cruel to people, it’s likely they will be cruel in return.

Like everything in this world, there are exceptions. If a stranger jumps you in a dark alley, it’s acceptable to kick them. You don’t have to be nice to people who are truly undeserving. If they’re mean to people, it’s likely people will be mean to them. Attacking people is illegal and it’s mean. But if you see an elderly lady struggling at a busy intersection, it’s unkind to honk your horn at them. The senior citizens in our culture don t move slowly to annoy you. Other religions had their laws translated over time, with dramatic differences, but the Wiccan laws and traditions have been translated into numerous languages throughout history, always with the same principles.