# [Japt], 8 bytes

    r"%d*$"V

[Try it online!][TIO-j3lagnsv]

# Explanation
     r"%d*$"V
    Ur"%d*$"V # Implicit input (U)
    Ur        # In the first input string, replace
      "%d*$"  #   0 or more trailing digits
            V # By the second input
              # Implicit output

[Japt]: https://github.com/ETHproductions/japt
[TIO-j3lagnsv]: https://tio.run/##y0osKPn/v0hJNUVLRSns/3@lxKRkJR0FJRNTMyUA "Japt – Try It Online"