Hi everyone, i'm trying to resolve an C exercise where i have to convert number into an intenger, and i'm trying to use a formula that i had found in internet, it's simple math but for some reason i keep having this same error:

solution.c:10:27: error: subscripted value is not an array, pointer, or vector
    binaryValue += ( value[i] * ( 10  length );
                     ~~~~~^~
solution.c:10:39: error: indirection requires pointer operand ('unsigned int' invalid)
    binaryValue += ( value[i] * ( 10  length );


This is the actual full code of function:

size_t countBits(unsigned value)
{
  unsigned int length = sizeof(value) - 1;
  unsigned int binaryValue = 0;
  
  /* Convert number into intenger */
  for ( unsigned int i = 0; i <= length; ++i )
    binaryValue += ( value[i] * ( 10  length );

 return binaryValue;
}

I'm just trying to multiply the first number in the int for the ( 10  length ) using the iteration number as index, someone knows how to resolve it?