How to Upgrade to existing SPFx v1.14.1 to v1.16.1 with compatible Node Js library upgrade,

Ashishiaf I will suggest to use the CLI for Microsoft 365 library for upgrading SPFx solution: spfx-project-upgrade 

Check these links for more information:

1. Upgrading SPFx solutions to the latest version using the CLI for Microsoft 365 
2. Update SharePoint Framework packages 

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