. How do I prove I was related to my deceased grandmother?

when people tell you in emails that you received an inheritance it's usually a scam so don't believe them. Now if you received a letter from a representative of the will of your grandmother and you know that person and you know the date they died and where, and other family members are listed on that document then you can expect a check. You don't have to prove you are her grandson because family would know you.

If on the other hand you want just to find out about this grandmother then contact the newspapers in Woodridge, NY and ask for the obituary of your grandmother telling them the day (or at least the month/year) she passed. Family should have listed you on that obituary or at least the names of your parents.

Tell people you are from poland

Maternal or paternal?

The easiest way is birth records. Your grandmother give birth to one of your parents, who gave birth to you. Simple.

The problem is, was there a will? If not, then it went to her children or the state.

Primary records, such as your birth certificate, shows your parents, their marriage cert the parent who was her childs birth cert shows proof of lineage.......... who she left the inheritance to is another thing as you may not be the heir anyway

Tell people you are from poland