How mlong would it take to dig a hole 10 m by 10 m by 10 m?

That depends on how quickly the hole is being dug. First, you have to find how many cubic feet this hole is. That's fairly simple; length times height times depth equals volume, so the hole is 1,000 cubic feet. Say you're digging at one cubic foot per ten minutes, then it would take you 10,000 minutes (166 hours, about seven days) so just under a week to dig a hole at that rate.