=c1&D1&E1&F1&G1

The &-sign serves as a concatenation marker.
This will work as long as each column has the correct number of digits.
If digits are truncated by zero suppression, you will have a problem.
One way to ensure the correct number of digits in each column would be to
use Data Validation to control manual data entry.
Column formatting to eliminate leading zero suppression would also help.