You need to make sure that your tables are properly joined in the query.
Something like:
SELECT
a.pType, a.sOnHand, a.DateModified,
b.wQuantity,
c.mcQuantity
FROM iParts a
join
iWSpares b
on
a.primary_key = b.foreignkey
join
iMSpares c
on
a.primary_key = c.foreignkey