To eat so many calories is challenging. What are very good sources are: peanut butter and any other nut butter (from almond, cashew, sesame, etc.), also cold pressed oils, avocado, nuts and seeds and fruits. Smoothies help to get quite an amount of calories in the body.
Also would be good for sure to eat fermented foods.
At the end, you are your best adviser as you feel what's good for you and what not.
Wishing you all the best! 🍀🙌🏼