unable to change nvarchar to datetime type

Sajj_Mak use only the valid left part together with CONVERT and the date sytle 126 = ISO,

DECLARE @date nvarchar(50) = N'2023-08-03T02:00:31+00:00'

SELECT CONVERT(datetime, LEFT(@date, 19), 126)

See CAST and CONVERT (Transact-SQL) - SQL Server | Microsoft Learn