import multiple csv files as list in R and change the name of one cell in each file

Question

I am searching since days but I can't find an answer to my question.

I need to change a single cell currently named "29" into "Si29" in hundreds of csv files. The position of the cell is the same in every file [3,7]. Then I need to save the files again (can be under the same name).

For one file I would do:

read_data[3,7]<-"Si29 

However, I have no clue how I apply this to multiple files.

Cheers