Hi @Krit60
Here is the sample flow that read the text file & update the text column.
Text file has been saved in the Document library inside the folder as shown below:

I have taken a SharePoint list 'SampleList' and Title is the column whose value will be replaced by content stored in text file.
Create an automated cloud flow and choose the trigger as 'When an item is added'. Set the SharePoint site URL & list name as shown below:

Next, add "Get file content using path" action to get the content of text file. Set the SharePoint site URL & the path of text file from which content need to be read:

Finally, to update the Title column with the value of text file content add 'Update item' action. Choose the ID & body of file from the dynamic content as shown below:

If this helps & solves your problem, please remember to give a 👍 and accept my solution as it will help others in the future.
Thanks