unable to use the main.terraform file due versions issue

[nsaarang]

unable to use the main.terraform file due versions issue as i am getting these errors

�[31m│�[0m �[0m�[1m�[31mError: �[0m�[0m�[1mMissing resource instance key�[0m
�[31m│�[0m �[0m
�[31m│�[0m �[0m�[0m on main.tf line 18, in resource "aws_s3_bucket_notification" "bucket_notification":
�[31m│�[0m �[0m 18: bucket = "${�[4maws_s3_bucket.lambda_trigger_bucket�[0m.id[count.index]}"�[0m
�[31m│�[0m �[0m
�[31m│�[0m �[0mBecause aws_s3_bucket.lambda_trigger_bucket has "count" set, its attributes
�[31m│�[0m �[0mmust be accessed on specific instances.
�[31m│�[0m �[0m
�[31m│�[0m �[0mFor example, to correlate with indices of a referring resource, use:
�[31m│�[0m �[0m aws_s3_bucket.lambda_trigger_bucket[count.index]
�[31m╵�[0m�[0m
�[31m╷�[0m�[0m
�[31m│�[0m �[0m�[1m�[31mError: �[0m�[0m�[1mError in function call�[0m
�[31m│�[0m �[0m
�[31m│�[0m �[0m�[0m on outputs.tf line 14, in output "s3":
�[31m│�[0m �[0m 14: value = "${element(concat(aws_s3_bucket.lambda_trigger_bucket.*.id, �[4mlist(�[0m"")), 0)}"�[0m
�[31m│�[0m �[0m
�[31m│�[0m �[0mCall to function "list" failed: the "list" function was deprecated in
�[31m│�[0m �[0mTerraform v0.12 and is no longer available; use tolist([ ... ]) syntax to
�[31m│�[0m �[0mwrite a literal list.