Shimano offer 10-speed road chains with 114 links or 116 links. I guess the first option may be too short for some triples, so they call it a doubles-only chain. But that depends on the actual size of cassette and chainstay length too, so 114 will actually be enough for most ‘racing’ triples, whereas 116 will be too short for some touring bikes with long chainstays. Some of my bikes need 118. I wouldn’t buy a Shimano chain anyway. Sram or KMC are my preference, because they come with a convenient and reliable re-joining link.
The standard length of an off-the-shelf derailleur chain used to be 120 links, but the bean counters got wise to that and nowadays only Sram offer a 10-speed chain that long, as a special for 29er MTBs. MTB 10-speed chain works just as well on road bikes.
What length do you need? Count the old one. If that’s in the bin, you can work it. Multiply the chainstay length in inches by four; then add the sum of the teeth on the biggest ring and biggest sprocket, divided by two; then add three; then round it up to an even number. For example: if the bike has 425mm (i.e. 163/4 in) chainstays and 50/32 big-and-big, then it’s 16.75×4 + (50+32)÷2 + 3, which is 67+41+3 = 111. Rounding up gets 112 links.