Convert a string to number in tabular format

We are using 18.1

We have a string that has comma separated values and few such rows exist in a csv file. We upload this file and then select each row and save in a string. The string's values(separated by comma) are then saved as an array . When we try to assign this array's each row 's first columns'f value to a number variable, the pl/sql code is erroring out saying that numeric to conversion error occured. This is happening even when I assign the row's first columns's value to the numeric variable using to_number() function since the value as stored