I am facing a problem and want to know the solution.

We had one portion house (building was made by my father whereas the land was of my cousin) and we converted it to an orphanage an year ago. Due to less resources, I had to raise donations to build the second portion of the house and renevote as well. Last year we completed it.

After one year of struggle we couldn’t run the orphanage successfully though we had couple of children. Now, we have to dissolve the orphanage (one of the reasons was that the cousin was asking for his property back).

I need to know, what I have to do for the donations I raised since we are not using the building for the purpose we renovated it. The problem is that I only have the data that how much donated money was used, but we don’t have the data of people who donated

You have to return the money to the people, or take their permission in using it in different project.
If the money was used to renovate the building, which added a value to the building, then your cousin should reimburse the donators. If you are not able to reach the donators, you should use the money in similar activity. i.e Donating to an orphanage