@Mateo Estrada Bazan Hello and welcome to Microsoft Q&A.
As I understand you want to partition the data coming from a third-party REST API and write it to Data Lake.
At first it sounde like you want to just break the data up into smaller files.
However a meaningful partition would partition on some aspect of the data. This assumes you are able to specify a query or filter to the REST API, like get family names where family size > 3.
You could then write all the expected filter values to an array variable and pass it to a ForEach activity. Inside the ForEach activity your copy activity uses those values to populate the filter / query to the REST API, and specify unique filenames in the Data Lake.
If you can't specify query / filter, and just want to break the data up into equal sized files, there is a way to do that. Have your sink dataset point to a folder and leave the file blank, do not point to a file name.
Then in the Copy Activity Sink tab, you can specify
Max rows per file.