If at could start at blank slate then base 12 would make a better foundation, but base 10 is far too ingrained into every aspect of our life. It's much easier to convert time into base 10 than it would be to convert the world into base 12.
I used to do it this way in highschool, but could never remember if it was divide by or multiply by 3.6
Instead I now do it as you have shown, except it all goes in the same expression.
10 km/h * 1000 m/km * 1h/3600s = 2.778 m/s
No need for the extra steps. Slap it all in the same expression and put it in the calculator (being careful to check that the units cancel as intended)
M/s is faster (lower number) than km/h so... That should give you enough explanation to understand whether you need to divide or multiply 3.6 when converting.