how to convert large bundt recipe to mini bundts

If you want a certain amount of mini bundts, you might want to consider testing the volumetric capacity of the large pan vs. the small pan. Sometimes there are resources online for that (usually standard pans), but you can also use measuring cup and water. If you don't really care how many bundts you get and you just plan on making a single recipe, I'd just say go for it and fill the mini pans ⅔ way full as Nancy suggested. There won't be any other conversion required other than baking time. I'd set the timer for 20 minutes, and then check on them every couple minutes after that until a skewer comes out with a little bit of moist crumb, but not batter.

The 10" Bundt pan recommended probably has 12 cup capacity.
Commonly, it is good to fill cake or muffin pans 2/3 with batter before baking (that would require about 8cup total batter).
Measure you mini bundt pan volume with water....
If you have a 6-indent mini bundt pan, 1 cup each, you'll need to bake half the recipe two times (2/3 cup batter in each of 6).
If your indentations are larger or smaller, adjust as needed.