as told above:
ArrString = String Array Default Value: new String(){Qty1,Qty2,Qty3,Qty4}
So you stored many strings within an array
For the type Into you will need a string
Depending on how the different items from the array are to separate we do need a flat string done with String.Join
String.Join(", " ArrString) ← here each item from the array will be separated by comma space