I have a spreadsheet with information stored on Sheets named St1, St2 and St3

The spreadsheet retrieves data from specific cells on the sheets and gathers
them on a summary sheet.

What I would like to do is be able to import St1, St2 and St3 from other
similar spreadsheets so that my spreadsheet can summarize these data sets.

So, I am asking if there is a way to import specific sheets from another
spreadsheet

I would also like to know if there is a way to export changed sheets to save
them as a new workbook? or better still update the spreadsheet from where the
sheets were imported from

Can anyone help