I would combine them into the full integer value in the PLC then read the single combined tag at the HMI.
Put a numeric label on the screen and select it.
In the Appearance area, find the “Number Format Pattern” entry.
Change it from #,##0.##
Technically, you don’t need the # values if you know it will never have a decimal. The Zeros tell it that no matter what you want those leading zeroes. That way you combine it in the PLC and format the display at the HMI to give you the total look you want.
If that’s not an option… well, you could do the same math at the HMI level. Make an expression tag. For the expression take the number that will be the left most entry and multiply it by 1,000,000,000, take the second left most group and multiply it by 1,000,000, multiply the 3rd group by 1,000, and finally take the current value of the right most group. Add this all together and bam, you’ve got the number you’re looking for. So if your tags were Num1, Num2, Num3, and Num4 the expression would look something like
(Num1 * 1,000,000,000) + (Num2 * 1,000,000) + (Num3 * 1,000) + Num4