To go to 11.x to 13.0.3 , follow these upgrade recomendations. Here’s an example upgrade path that should work for you:
11.x -> 11.11.8 -> 12.0.12 -> 12.10.8 -> 13.0.3
Using apt package manager to specify version to install:
apt install gitlab-ce=11.11.8-ee.0
apt install gitlab-ce=12.0.12-ee.0
apt install gitlab-ce=12.10.8-ee.0
apt upgrade gitlab-ce