As a Canadian who was raised on the metric system.... I primarily think in feet and pounds. I have no idea how to help you.

One thing I guess is that I never found feet and pounds to be hugely important. The weight of things is usually for carrying capacity but I've found two systems I like more than that and so that is a non-issue for me. And for distances - well that one is trickier but I don't find it comes up very often either. Except for the movement of people - 30 feet, 25 feet, 20 feet - which can be converted to meters either straight calculator conversion (before play), or by swapping the feet into yards and then to meters as a rough estimate (during play), or by ignoring the issue entirely (keeping as it is?). Especially if going for theatre of the mind, I don't see the problem. I can't visualize 30 feet, 10 yards or 10 meters (and I think primarily in feet and inches) but I know 30 feet is the movement speed of a medium creature, so I use it as a measurement. Otherwise it doesn't really come up too often in TotM.

Be careful if converting to meters and then running a grid, it will mess with things - especially on littler creatures and their distance traveled. For quick conversion 30 feet becomes 10 squares, but 20 feet has to be rounded to 6 or 7 (20/3 = 6 and 2/3) and 25 is just over 8 (8 and 1/3) which doesn't create a nice scale to movements. I don't even want to think what it would look like for straight mathematical conversion.

I wish they did distances in yards though, so much more elegant for this conversion and for visualization (apparently). Even for the sizes of spaces for creatures (my favourite reason).

So, tl/dr - no idea really, sorry. But I wouldn't really worry about trying to convert it.