Recommend me a training plan for a climbing event,please

Hello everyone. On July 7th I will take part in the Maratona Dles Dolomites event in Italy. I want to cycle the maximum route Length: 138 km with Altitude gain: 4230 m. Now I’m in bad shape, I haven’t trained for a long time and I set myself the task of preparing for the event. What program would you recommend? Last summer I completed the “Build me up” program. Good program, quite complex.