You can look at the back side of the backing plate to count bolts. No need to pull the drum.
PS: Your'e not that far from me, If you need help or parts, contact me in a "conversation". I'll give you my address and phone number.
It is a 4 bolt plate. I will pull the axles and install the new ones. I have dual pattern 9” drums to go with the new axles. Looking forward to having matching 15” wheels all round. Thanks for the help.