You can use TStringHelper.Split.
procedure TForm2.Button1Click(Sender: TObject);
const
SrcString : String = '2090Lj32J5Y6Ni6Q2Rt8c538u1X227L340Q8N1...ce4A3z6l96S5v7LZ3OhSVoB538k7wPTn13E2w2D0h104fJ7HP09xo7W71J1o02c088922A3t420697F5431XP91C6JF9w1Ss0Tuk5S669207816gp57pW193BPWL27AZ052nr2S714...30';
Delim : String = '...';
var
S : TArray<string>;
begin
S := SrcString.Split(Delim);
Memo1.Lines.AddStrings(S);
end;