First, you will need to decide which country you want to choose for the conversion.
It's all EASA, but some interpret the regulations a bit differently from others... Plus flying time is cheaper in some...
Then, you will need to go through a flight school.
It's not possible to do this without a flight school.
The school will determine whether you require additional training, or if there is no training requirement due to your experience.
Best case, you only need to pass the exams, get a medical, and do a check flight in order to get the type rating on your easa license.