this is what I found that helped me: I recently had a project where I needed a counter to go from 1 – 1,061.
https://www.videocopilot.net/forum/viewtopic.php?f=5&t=17819
taken from the above link:
Formatting a number with commas
1. Create a comp. Name it anything you like.
2. Create a new text layer and name it “dummy” (this layer can be turned off; it feeds a number to the final text layer. I haven’t found a way around this; please let me know if there’s another way).
3. Add a slider to the “dummy” layer (Effects > Expression Controls > Slider Control). After Effects should automatically name the slider control “Slider”
4. Add an expression to Source Text of “dummy” (Animation > Add Expression).
5. Pickwhip the expression to the “Slider” control from step 3.
6. Create a second text layer. This will be the layer that displays the formatted number.
7. Add an expression to Source Text of the new text layer. Replace the code with the following:
var num = thisComp.layer(“dummy”).text.sourceText;
num = Comma(num);
[num]
function Comma(number)
{
number = ” + Math.round(number);
if (number.length > 3)
{
var mod = number.length % 3;
var output = (mod > 0 ? (number.substring(0,mod)) : ”);
for (i=0 ; i < Math.floor(number.length / 3); i++)
{
if ((mod == 0) && (i == 0))
output += number.substring(mod+ 3 * i, mod + 3 * i + 3);
else
output+= ‘,’ + number.substring(mod + 3 * i, mod + 3 * i + 3);
}
return (output);
}
else return number;
}
Now try changing the value of the “Slider” control. Your visible text layer should reflect that number, now formatted with commas. Two catches: it only works for integers, and the slider tops out at 1,000,000. You should be able to pickwhip to any propery that contains a number (decimals are rounded off automatically).