Issue with output text. Displaying all zeroes. File I/O.

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C

The program is the start of a program that will read a file consisting of two columns of
data. This is my current data text in which these values will be outputted and rearranged.
1 2
3 4
37 45
36 90
2 32
4 56
12 72
65 38
12 98
34 45
6 45
78 29

the rows and columns are printed out with the columns switched. Upon running my code I receive 0s in both columns. I think my issue is data1 and data2 variables need to be replaced with the appropriate array location, but I'm stuck on how to solve this.
Here's my current code; I cannot make any modifications to the code except within the while loop; which I think is fine partially but has an issue correctly reading my text values. Here's my code; 
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
	
	if (argc != 2 ) {
		
		printf("%s filename\n", argv[0]);
		exit(0);
	}
	FILE *fp = fopen(argv[1], "r");
	if (fp == NULL) 
	{
		perror("Could not open file");
		exit(0);
	}
	int num_rows = 0;
	int num_columns = 2;
	int *column1 = malloc(10 * sizeof(int));
	int *column2 = malloc(10 * sizeof(int));
	int data1;
	int data2;
	int retval;
	while (1) 
	{   
		int retval = fscanf(fp,"%d %d\n", &data1,&data2); 
		if(retval==EOF) 
				break; 
			num_rows++;
			if(num_rows%10==0)
				column1 = realloc(column1, (num_rows + 10)*sizeof(int));
				
					
	}
	int i;
	for (i=0; i<num_rows; i++) {
		printf("%d ", column2[i]);
		printf("%d\n", column1[i]);
	}
	
}

What I have tried:

I've tried setting a char*filename = argv[1] but this has not worked.