Hi my name is yogesh , I have problem in solid works how to convert from surface model to solid model please suggest me.

Surface / Knit Surface / Assigned all surface (Have to be a closed surface / solid part) / Click to " Try to form solid" / Ready

hello yogesh...there is a tutorial available in your solidworks regarding the surface.try to study that tutorial and i think it would be the answer to your question. i have here the attachment that might help you get in there.

You should first join all surface by join command and heal it such that it will be fully closed. If limit of merging distance is greater then extract near by surface and create advanced surface tool like blend to minimize distance and then join all extracts and include in modified healing

If you have a gap between surfaces you should fill up with "Filled" or "Boundary" commands! Gap is not allowed. In this case you are not able to use join command. Join is a Feature command not a surface command.