[middle 1 of 3d10] means (for anydice.com) that you roll three d10s and pick the middle value. E.g., you roll a 2, a 4, and a 7, so the result is 4.
[middle 1 of 3d10]*10 makes that the tens digit. E.g. you roll the 2, 4, and 7, it picks the 4, and then multiplies by 10 to get 40.
Then add the 1d10 for the ones place. So if you had 40 at the previous step, and then roll a 6 on the last 1d10, the result is 46.
I am pretty sure that is how to express the die rolling mechanic you are suggesting. If you paste the whole thing into the box at anydice.com, click Calculate and then click Graph, you'll see a plot of the resulting distribution.
There's one quirk that these are really 0-9 dice and not d10s, but 00 means 100. I ignored that with the result the curve is offset 10 to the right. The shape is still correct. If you want to correct for that (except the 00 result), you can use this instead:
output [middle 1 of 3d{0,1,2,3,4,5,6,7,8,9}]*10 + 1d{0,1,2,3,4,5,6,7,8,9}
There's a way to fix 00 but I stopped before I figured that out.