Failed to call hook 'OnNewSave' on plugin 'Backpacks v3.7.2' (DirectoryNotFoundException: Could not find a part of the path 'C:\Users\AVALANCHE\Desktop\Rust_Server\1Zombie_Experiment-staging\oxide\data\Backpacks'.)
  at System.IO.__Error.WinIOError (System.Int32 errorCode, System.String maybeFullPath) [0x000f7] in <fb001e01371b4adca20013e0ac763896>:0
  at System.IO.FileSystemEnumerableIterator`1[TSource].HandleError (System.Int32 hr, System.String path) [0x00006] in <fb001e01371b4adca20013e0ac763896>:0
  at System.IO.FileSystemEnumerableIterator`1[TSource].CommonInit () [0x00054] in <fb001e01371b4adca20013e0ac763896>:0
  at System.IO.FileSystemEnumerableIterator`1[TSource]..ctor (System.String path, System.String originalUserPath, System.String searchPattern, System.IO.SearchOption searchOption, System.IO.SearchResultHandler`1[TSource] resultHandler, System.Boolean checkHost) [0x000d6] in <fb001e01371b4adca20013e0ac763896>:0
  at System.IO.FileSystemEnumerableFactory.CreateFileNameIterator (System.String path, System.String originalUserPath, System.String searchPattern, System.Boolean includeFiles, System.Boolean includeDirs, System.IO.SearchOption searchOption, System.Boolean checkHost) [0x00009] in <fb001e01371b4adca20013e0ac763896>:0
  at System.IO.Directory.InternalGetFileDirectoryNames (System.String path, System.String userPathOriginal, System.String searchPattern, System.Boolean includeFiles, System.Boolean includeDirs, System.IO.SearchOption searchOption, System.Boolean checkHost) [0x00000] in <fb001e01371b4adca20013e0ac763896>:0
  at System.IO.Directory.InternalGetFiles (System.String path, System.String searchPattern, System.IO.SearchOption searchOption) [0x00000] in <fb001e01371b4adca20013e0ac763896>:0
  at System.IO.Directory.GetFiles (System.String path, System.String searchPattern) [0x0001c] in <fb001e01371b4adca20013e0ac763896>:0
  at Oxide.Core.DataFileSystem.GetFiles (System.String path, System.String searchPattern) [0x0000c] in <bae5f1223fce49c493b01571c99dce02>:0
  at Oxide.Plugins.Backpacks.OnNewSave (System.String filename) [0x00032] in <db1db214bf8047d48442505bf15681ad>:0
  at Oxide.Plugins.Backpacks.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x001e9] in <db1db214bf8047d48442505bf15681ad>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <09575a60985045248bcb43b20faeeb99>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <bae5f1223fce49c493b01571c99dce02>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <bae5f1223fce49c493b01571c99dce02>:0

The error means your path doesn't exist. Did you remove the folder? Did you change the path at all?

C:\Users\AVALANCHE\Desktop\Rust_Server\1Zombie_Experiment-staging\oxide\data\Backpacks