i don't know of a spell that'll tell you if they're your soulmate or not, but i do have one simple spell to find out if they like you, i've never tried it before so i can't guarantee it's success
cast during a full moon on a friday, need 1 red rubber ball, concentrate and focus your energy on the ball, when you're ready, bounce the ball and chant
"from ground to air, from air to ground, I bounce the magic round and round. do you like me? do you love me? I need to know the answer. Dragons eyes and angels wings. now I touch the fairy ring. do you like me? do you love me? i need to know the answer. earth and air. fire and water. my little ball goes higher and higher. mine is magic, mine is power. it is time i know the answer."
keep bouncing and say 8 times
"with harm to none as I will it shall be done. may all astrological correspondence be correct for this working, and may this spell not reverse or place upon me any curse. so mote it be."
never did find out if the answer will come to you in a dream, or they'll tell you, but you could try that, it's rather simple. i might have a couple others kicking around, but i've got so many it'll take a while