Scripts expects https://github.com/Tyrrrz/DiscordChatExporter to be installed in the folder under DiscordChatExporter and dotnet CLI to be installed as well.
Read here how to obtain Discord's token: https://github.com/Tyrrrz/DiscordChatExporter/wiki/Obtaining-Token-and-Channel-IDs
dotnet ./DiscordChatExporter/DiscordChatExporter.Cli.dll dm -t "token" > ./input/channels_dm.txt
dotnet ./DiscordChatExporter/DiscordChatExporter.Cli.dll channels -t "token" -g "server_id" > ./input/channels.txt
Run node export to export data from your Discord Server (you will need to provide either input/channels.txt or channel ids to use)
Run node convert to prepare output dir (you will need to provide either input/channels.txt or channel ids to use)
Archive output and upload it to Slack Import Tool
This is not ready to use scripts, if you need help, please create issue or PR.