Hi Everyone, I need to know from whom I can get the Letter of recommendations

I have a bachelor's in Mechanical Engineering and planning to do a master's in Computer science. I am planning for the 2023 Spring intake and I have 4.5 years of work experience in CS. I have below questions regarding the letter of recommendations.
1. Do I need to ask LOR from the lecturers?
2. Since I studied mechanical Engineering will the LOR from the Mechanical lecturer help?
3. I can get 3 LOR from my workplace from my leads and Manager. If I submit 3 LOR from them is that enough?

Thanks.

#masters