If your paintings have signatures you can research them yourself by using the free to access listings on findartinfo.com and liveauctioneers.com. This will at least give you some idea as to whether you have paintings by listed artists whose work has already passed through auction.
Please bear in mind that only a tiny fraction of pre-owned art is worth large sums of money. That said, rare and valuable items are uncovered every day. Your collection might include some of them.
The best way to find a likely value for your paintings is either to take them to an auction house, or else to take them to one or more art dealers. Nobody will oblige you to sell your art this way. You always have a choice. Listen to what the experts have to say, and then decide which route is best for you. Do remember to check the amount of commission you will have to pay if you do decide to take the pictures to auction.