@moriombegum I do not believe you will find a lens to repair your camera. You will need to replace the whole camera. Since your phone has four different cameras it will help if you let us know which camera is giving you problems. Since iFixit does not yet have any guides for this, I'd suggest you check the guides [https://www.nadiemellamagallina.com/en/manuales/smartphones-1/poco-1304/poco-m3-1283/|on here] They are written in Spanish so use a browser that does the translating for you, if needed.
While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.
Repair is War on Entropy!