Q:

take in user input, search where its range value lies in array and return the row index of the 2d array

This is my 2d array with available speeds listed. this code I must keep. If my user enters 75349 as their clock speed input, how will I be able to recognize that speed and return the value of the row index ?... which is row 2 int the 2d array because it lies between 7500- 14900
int UserClockSpeedInput;
const uint32 SpeedTable[5][2] {
{15000, 99990}, //between 15k - 99.99k
{7500, 14900}, //between 7.5k - 14.9k
{3500,7400},
{1900,3400},
{6000,1800}
}

I want to return the row index of whatever value the user entered, 
these are the set values I already set in place. They are not allowed to enter any other values
for(i=0;i<5;i++)
{
    for(j=0;j<2;j++)
    { 

 //not sure of what to do from here.

A:

how will I be able to recognize that speed and return the value of the row index 

Solution :
You can simply achieve it by using the following for loop
    int number; //variable to hold user's input

    //scanning user's input
    printf("enter any number : ");
    scanf("%d",&number); 

    //for loop to determine position
    for (int index = 0; index < 5; index++)
    {
        if( (number >= SpeedTable[i][0]) && (number <= SpeedTable[i][1]) )
        {
            break;
        }
    }

    //printing index
    printf("return index value : %d ",i);

Suggestions :
firstly,

I think your last element of the 2-D array must not be {6000,1800}, 
I think it must instead be {600,1800}

and,

Don't use void main(). to know why, see this : click
Instead use int main(void). to know why, see this : click

so altogether your code would be :
#include <stdio.h>

int main(void){

    const unit32 SpeedTable[5][2] = {
        {15000, 99990}, //between 15k - 99.99k
        {7500, 14900}, //between 7.5k - 14.9k
        {3500,7400},
        {1900,3400},
        {600,1800} //between 0.6k - 1.8k
    };

    int number;

    printf("enter any number : ");
    scanf("%d",&number);

    int i;

    for (i = 0; i < 5; i++)
    {
        if( (number >= SpeedTable[i][0]) && (number <= SpeedTable[i][1]) )
        {
            break;
        }
    }

    printf("return index value : %d ",i);

}

