after signing into cloud I am unable to increase my storage from 5 GB to 200 GB

Hi charu198,

welcome to the Apple (user-to-user) Community

Re: "cloud: unable to increase my storage from 5 GB to 200 GB"

Apple support have a video online that may help guide you:

How to upgrade and manage your iCloud storage on iPhone or iPad

https://www.youtube.com/watch?v=RcqL6JqyJQQ

or scroll dow to:

"Manage your iCloud+ subscription on your Mac" in the article below:

Upgrade to iCloud+ and manage your subscription - Apple Support

If needed: You can contact iCloud Support:

iCloud Support Website: info / support / contact etc.

(There is a "Get Support" link (online chat, phone, eMail etc) at the bottom of their webpage (link below):

iCloud - Official Apple Support

All the best :-)