Hey,
I am providing a link below which has a sample letter of recommendation for graduate admissions, MBA, medical school, etc.

• Make sure your grammar and spellings are correct.
• Keep it upto 1 page. And always do proofreading.
• Do not use social media words. Be formal.
• Write a good introduction and it is important to end the letter with a appropriate closure.

https://www.google.com/amp/s/studyabroad.careers360.com/articles/letter-recommendation-sample-download/amp

You can download the samples from here and write it down on your own.
Or you may also find templates in the Microsoft word application.

Hope this helps!