AZ Jane, open your machine and look at the bobbin that's in it now. Then put all the same bobbins in something (I use round candy cans for mine). Then I take painters tape and I list the machine these bobbins will fit in and if the bobbin is metal, plastic and how many holes are in it. I've done the for each of my machines (I have 6), because I had problems too. Then when I'm working with a machine, I pull said can to keep close as I work for changing colors etc...
That's what works for me