Snap sentinel 1 graph building

in my graph builder read operator is not present what should i do

You can click on clear in the lower row of buttons. This will erase the nodes already added to the graph.
Afterwards you can add the read and write and also other nodes again by using the right-click context menu.

Maybe this resolves already the issue.
If not, it would be helpful if you provide the log file. It is explained here:
See: FAQ - Read This Before Posting