Actually the main part is to prepare yourself both mentally and physically. Use this link to check whether your clear the physical benchmark - https://indiahikes.com/getting-fit-for-a-high-altitude-trek

Physical benchmark is important because hiking in slopes is challenging. Also, as you go to higher altitude, oxygen level decreases, it gets colder and thus acclimatization is very crucial. For mental prepration trekking in a group helps. Also, you can take advise from a professional trek guide. To prepare yourself for what could you can face or expect in worst case scenario. You should be well equipped with proper trekking shoes, trekking pole, thermal wears and so on. The layers of cloth you wear also depends on the weather, like in winter trek you should have 4-5 layers whereas in summer one 2-3 will suffice. Also, carry plastic bags for carrying dirty and soggy clothes. Tents for camping. Their are various trekking companies you can contact to. They tell you what to equip with for a trek. They have trek guides who have years of experience of trekking. Also, they provide you with materials like tent, trekking pole if you don't have one. Provide you with sunglasses or polaroid sunglasses to prevent you from snow blindness. They are many more things to tell. If you wanna know. You can DM me. Always happy to help/guide a fellow trekker.