Q: Just Migrated to swift 5 from swift 3. How to fix the following errors? Just Migrated Swift 3 to Swift 5 and getting all these errors. I had no errors before doing this.
var imageData = UIImageJPEGRepresentation(imgTemp, 1)  

ERROR: 'UIImageJPEGRepresentation' has been replaced by instance method 'UIImage.jpegData(compressionQuality:)'
tableView.SeparatorStyleCell.none

ERROR: Value of type 'UITableView?' has no member 'SeparatorStyleCell'
tableView.UITableView.AutomaticDimension

ERROR: Value of type 'UITableView?' has no member 'UITableView'
self.tableView.UIEdgeInset  = insetsMake(8, 0, 15, 0);

ERROR: Use of unresolved identifier 'insetsMake'
attributedString.addAttributes(boldFontAttribute, range: datetime.range(of: "Read"))

ERROR: Use of unresolved identifier 'boldFontAttribute'

A: Hi @Brett Taylor.
The errors your are getting are a mix of compiler telling you the syntax you are using is outdate for this version of Swift, e.g.:

'UIImageJPEGRepresentation' has been replaced by instance method 'UIImage.jpegData(compressionQuality:)'

and the Swift migrator doing something funny with your code, e.g.:
self.tableView.UIEdgeInset  = insetsMake(8, 0, 15, 0);

Have you got that code under version control? Ideally a Git repo?
If so you can revert all those changes and start again. Or just set the version of Swift to 5 without using the migrator and solve each compiler error as it comes.
The best thing to do is to tackle one error at a time, and maybe make a commit every time you solve something, so you can start back from there if the next step doesn't workout, without having to loose all your progress.
For the messed up code, maybe you can just get an idea of what the code was doing before, and try to re-write it from scratch.
In the example above, I'm guessing it's code so set the content inset or some other inset property of the table view. You could re-write it like this:
tableView.contentInset = UIEdgeInsets(top: 8, left: 0, bottom: 15, right: 0)

Note that I removed the self., it's usually not necessary unless you are inside a closure and you need to make it explicit.

A: Looks like some orphaned Objective-C managed to survive in your project.
tableView.SeparatorStyleCell.none

should be
tableView.separatorStyle = .none

Next:
tableView.UITableView.AutomaticDimension

should be
tableView.rowHeight = UITableView.automaticDimension

As for:
var imageData = UIImageJPEGRepresentation(imgTemp, 1)  

The old C function did move the class it was working with. (I like the way how Apple cleaned up the old interfaces)
var imageData = imgTemp.jpegData(compressionQuality: 1)

As for:
self.tableView.UIEdgeInset  = insetsMake(8, 0, 15, 0);

mokagios answer is right. Again its a clean up on Apples interfaces. UIEdgeInsets is now a type and has an init function.
Lastly:
attributedString.addAttributes(boldFontAttribute, range: datetime.range(of: "Read"))

I guess your boldFontAttribute is a Dict containing the corresponding key and Font. Unlike other attributes like Underline, is Bold not an Attribute, but a Font. To make a range Bold, you need to assign a different font to the range.
In Swift it would be 
let boldFontAttribute = { NSAttributedString.Key.font : YourBoldFont }

