Hi Surendra 

Thanks for reaching out in the Lucidchart Community! You can change the scale of your floorplan by clicking the gear icon on the bottom left corner of the canvas. You can then set the default unit as meters or feet for your scale and type the appropriate proportions in those units. In the image below the scale indicates that 1 inch of the canvas page equals 8 feet.

Please keep in mind that if you would like this scale to be apparent upon export you will need to add a measurement object to serve as a visual reference.

The wall length can be by dragging them to a specific size but there is not a way to type in the length. We’re very interested in your feedback and committed to continually improving our products. If you’re willing to share, we’d love to hear more details about your use case or what you’d like to see in this experience posted in the Product Feedback section of the community - from here, other users can upvote it and add details of their own. For more information on how Lucid manages feedback via this community, take a look at this post.

For more information on how to get the most out of our floorplan functionality please take a look at the Create floor plans to scale article from the Lucidchart Help Center.

Hope this helps! Please let me know if you have any further questions.