Is it me or is it so hard to find an entry level job when you are 40+ with no college degree and over 20 years work experience in another field?

I’m trying to find a job where I can work at least 20 more years till I’m 65. I have over 20 years experience in one field and the jobs are dwindling so I need a new career. I feel like I need to go back to school but which field do I choose that is going to give me a good chance of being hired. I’m so confused and frustrated.