I want to migrate yoast free to premium any please advise me is worth for money or not
NO!. I used yoast premium for one year and it is not worth it. If it was one time payment then yes but you have to renew every year.
I dont think its worth it.
Pay some freelancer and get better articles out there.
It helps more in ranking than a seo plugin.
See i totally believe keyword density , adding longtail keyword to check viability is a thing of past.
I have many posts where my subheadings gets ranked and win snippets.
I dont even use or optimise yoast to get green score.
Have long thorough content and you will rank good!
If you want SEO Yoast Premium features, Rankmath is the best Alternative option, you can get premium features without paying any single penny. might tryout.
Yes, RankMath is very good and is free also.