How do I pass the function argument in arduino?

I'm trying to control velocity in a motor via writing register value in microcontroller.

unsigned long PrintHex32( uint32_t data) // prints 32-bit data in hex with leading zeroes
{
  uint32_t data2 = data << 8;
  char tmp[16];
  uint16_t LSB = data2 & 0xffff;
  uint16_t MSB = data2 >> 16;
  unsigned long ppsval2 = sprintf(tmp, "0x%.4X%.4X%", MSB, LSB);
  Serial.println(tmp);
  Serial.println("***************");
  return tmp;
}
void NoRamp() {
  Serial.println("No Ramp");
  unsigned long ppsVal = (VMAX * FS * uS);
  unsigned long   ppsVal3 = PrintHex32(ppsVal);
  Serial.println(ppsVal);
  Serial.println(ppsVal3);
  Serial.println("$$$$$$");

  //********* NO Ramp **********////////
  sendData(0xA0, 0x00000000); //RAMP Mode
  //  sendData(0xA4, 0x03E80000); //VMAX-5rps/5hz
  //  sendData(0xA4, 0x00c80000);
  sendData(0xA4, ppsVal3); //VMAX-1rps/1hz

}

at the end i need to be send data format after hex conversion sendData(0xA4, 0x00c80000)

but currently, I'm getting my print output:

No Ramp
0x00C80000
***************
51200
0
$$$$$$

umm where do I making the mistake? Can anyone kindly slam my head a bit please! Thanks heaps!!

PS: also senddata method take below argument if anyone needs to know!

unsigned long sendData(unsigned long address, unsigned long datagram)

Edit: I think I can understand the proper question to ask?

unsigned long PrintHex32( uint32_t data) // prints 32-bit data in hex with leading zeroes
{
  uint32_t data2 = data << 8;
  //char tmp[16];
  uint16_t LSB = data2 & 0xffff;
  uint16_t MSB = data2 >> 16;
   unsigned long  val = xxxx(uint16_t LSB) + uint16_t MSB(YYY);
  //sprintf(tmp, "0x%.4X%.4X%", MSB, LSB);
  return val ;
}

if you can see im converting my input data2 to hex using uint16_t LSB and uint16_t MSB. how do i save that two value as one single unsigned long val . then I can return the that varible. I think using sprintf method is wrong as it does show just char representation? please kindly correct me this if im wrong?

The xxxx in the edit should probably be 2^16 aka 65536:

#include <cassert>
using namespace std;

int main(int argc, char * argv[]) {

unsigned int data2 = 12345678;
uint16_t LSB = data2 & 0xffff;
uint16_t MSB = data2 >> 16;
unsigned long  val = (1<<16) * MSB + LSB;
unsigned long  val2 = 65536 * MSB + LSB;
assert(val == data2);
assert(val2 == data2);
}