Not able to find the proper issue field

There are two key issues indicated by the error:
Data Type Mismatch
The source column contains a String value that cannot be converted to the target column’s nvarchar type.

This usually happens when:
The source data type is incompatible with the target schema.
There is an implicit conversion that fails (e.g., numeric string to nvarchar with                constraints).

String or Binary Data Would Be Truncated
The target column’s length is smaller than the incoming data.

For example:

Target column defined as nvarchar(50) but source value is 100 characters.

This is a classic SQL error when inserting or updating data.

Validate Target Schema

Check the target table column definitions in SQL:

SQL

SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH
FROM INFORMATION_SCHEMA.COLUMNS

Ensure the column receiving the data has:

Correct data type (e.g., nvarchar for text).
Sufficient length to accommodate source data.

Adjust Column Size
If truncation is the problem, increase the column size:

SQL

ALTER TABLE <TargetTableName>

ALTER COLUMN <ColumnName> NVARCHAR(500); -- or appropriate

Validate Source Data

Check if any source fields contain unexpected values (e.g., very large strings or invalid characters).

Apply data cleansing or mapping in your pipeline:

Use Derived Column or Mapping Data Flow in Azure Data Factory to:

Trim strings.
Convert data types explicitly:

SQL

CAST(<ColumnName> AS NVARCHAR(500))

Enable Detailed Logging

• In Azure Data Factory, enable Data Flow Debug or Activity Logging to identify which column is failing.
• This will help pinpoint the exact column causing the issue.