What spell or practice can i use to find out if a certain person is my soulmate? This is not violating free will since i am not using magic to make this person ask me out or love me. I just wanna know if someone who i think might be my soulmate is.
I wouldn't use a spell, but I would advise you to look into divination.
Pendulums can be tricky due to micromovements we make with our fingers, as well as the breeze, so I wouldn't really use those. There are many different types of divination, such as runes or tarot cards. You should see which will work best for you while still being accessible.