Measure the diameter with a digital caliper if you have, 30 caliber will be close to .308, 38 will be close to .357. Also weigh it on a digital scale in grains.
30 caliber is .308 Give or take a thou or two. Some bullets can be bought in slightly different size, 45 pistol bullets can be .451 or .452 depending on the type of gun you are loading them for.
Use the info you have and go to Midway USA for modern bullets. You can usually figure out what you found off their web site. Or take it to a local gun shop that sells reloading supplies.