Is the data is located in a DB or a directory?
If the data is in DB, it can be accessed from outside that PC through the IP addresses.
If the data is located on a directory, you can mount the directory(using folder mounting software that you have to install on the PC) with AWS S3 bucket, and then access the files through the S3 bucket.
The solution can be divided in 2 parts.
Mendix app can fetch data from the APIs and also post data back to the source through APIs.
This is high level generic solution, and will need change depending on the current details.