ForEachLoop not incrementing every cycle?

So i am coding a game and i thought that it would be more effecient to do the blueprints outside of each level and have them call on them instead. I am now facing an issue with the fact I cannot loop my level names. For example, i have level 1 open, then at the end of all the blueprints it would open the next level (level 2), but how would i have it do this multiple times with many levels so it opens level 3 and so on. I have attatched how i am currently doing it, but it doesn’t work. Any help would be greatly appreciated, thank you.

The array called integer index has the values of 0, 1.
The variable blueprint 1 has the value “blueprint_1” (Level 2)
The variable blueprint 2 has the value “blueprint_2” (Level 3)

Use the Append node to combine part 1 of the string to part 2