Hello @Karikalan Ramakrishn and thanks for reaching out. You can find samples for Azure AD B2C JIT migration in GitHub.
Although the sample code is written in C# it relies on ADAL and AAD Graph which are deprecated. Please replace references to former found in AzureADGraphClient class with proper ones from MSAL.NET and MS Graph .NET SDK.
Also, to write the migration API in other programming languages like JavaScript, Java or Python is pretty straight forward provided endpoints included in the UserMigrationController class are migrated and the appropriate MSAL and MS Graph SDK are used.
Let us know if you need additional assistance. If the answer was helpful, please accept it and complete the quality survey so that others can find a solution.