How much money can you get at a pawn shop to loan me for a 300 dollar item?

Roughly? Most likely $50 to $150 dollars depending on the item and possibly your customer record (amount of redemptions vs. the amount of items lost). On items other than gold a pawn shop will usually try to get anywhere between at least at 40% to 150% return, making the loan amount come out to generally a third or less of the items projected resale value.