It is almost a guarantee that you won't be able to model the whole protein except by using AlphaFold. Also, pretty much a guarantee that there is no free service out there that will let you model a ~4500 protein. A quick scan of PDB indicates that there is no template that covers even close to the whole protein. You should verify this last statement.
That leaves you with two options: find the domain organization of this protein and split it into smaller chunks, than model each of them separately with AlphaFold on Colab. You can try to model with Modeller, but you will most likely have to split the protein again since there is no continuous template for this protein. In case you don't know, Modeller can only do homology-based modeling (unlike AlphaFold, which doesn't require modeling templates). The latter option assumes you know how to use Modeller, which is not easy even for proteins of regular size.
How familiar are you with various protein structure modeling/prediction approaches?