Gravestone inscriptions carved before 1980 are generally inscribed by hand. Stonecutters used a hammer and chisel, not a sandblaster. Sometimes they relied on templates or lettering guides, but rarely printer’s fonts as we know them. So, this is very likely not a font. If you can, I would hire a professional stonecutter to do your parents’ stone — a good craftsperson can replicate the existing style.
If you must use a font, there are several that have similar qualities, but none will match all the letter shapes: