I went on to play Minecraft today and once I joined the world I got this message/error,

22:34:46] [Client thread/INFO]: Setting user: Cheetah0307
[22:34] [Client thread/INFO]: (Session ID is token:36b9fbb2d0524084af4f7cb79c7cbc36:36963ae7eaba4e58aab1a0ad153404b8)
[22:34] [Client thread/INFO]: LWJGL Version: 2.9.4
[22:34] [Client thread/INFO]: Reloading ResourceManager: Default
[22:34] [Sound Library Loader/INFO]: Starting up SoundSystem...
[22:34] [Thread-6/INFO]: Initializing LWJGL OpenAL
[22:34] [Thread-6/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[22:34] [Thread-6/INFO]: OpenAL initialized.
[22:34] [Sound Library Loader/INFO]: Sound engine started
[22:34] [Client thread/INFO]: Created: 512x512 textures-atlas
[22:34] [Client thread/ERROR]: Exception reading C:\Users\Emily\AppData\Roaming\.minecraft\saves\Parkour In Every Color 2\level.dat
java.util.zip.ZipException: Not in GZIP format
at java.util.zip.GZIPInputStream.readHeader(Unknown Source) ~[?:1.8.0_91]
at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.8.0_91]
at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.8.0_91]
at dx.a(SourceFile:13) ~[1.8.9.jar:?]
at atn.c(SourceFile:62) [1.8.9.jar:?]
at atk.b(SourceFile:52) [1.8.9.jar:?]
at axv.f(SourceFile:87) [1.8.9.jar:?]
at axv.b(SourceFile:59) [1.8.9.jar:?]
at axu.a(SourceFile:376) [1.8.9.jar:?]
at ave.a(SourceFile:819) [1.8.9.jar:?]
at aya.a(SourceFile:238) [1.8.9.jar:?]
at axu.a(SourceFile:350) [1.8.9.jar:?]
at aya.a(SourceFile:495) [1.8.9.jar:?]
at axu.k(SourceFile:413) [1.8.9.jar:?]
at axu.p(SourceFile:390) [1.8.9.jar:?]
at ave.s(SourceFile:1498) [1.8.9.jar:?]
at ave.av(SourceFile:889) [1.8.9.jar:?]
at ave.a(SourceFile:325) [1.8.9.jar:?]
at net.minecraft.client.main.Main.main(SourceFile:124) [1.8.9.jar:?]
[22:34] [Client thread/ERROR]: Exception reading C:\Users\Emily\AppData\Roaming\.minecraft\saves\Parkour In Every Color 2\level.dat_old
java.util.zip.ZipException: Not in GZIP format
at java.util.zip.GZIPInputStream.readHeader(Unknown Source) ~[?:1.8.0_91]
at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.8.0_91]
at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.8.0_91]
at dx.a(SourceFile:13) ~[1.8.9.jar:?]
at atn.c(SourceFile:73) [1.8.9.jar:?]
at atk.b(SourceFile:52) [1.8.9.jar:?]
at axv.f(SourceFile:87) [1.8.9.jar:?]
at axv.b(SourceFile:59) [1.8.9.jar:?]
at axu.a(SourceFile:376) [1.8.9.jar:?]
at ave.a(SourceFile:819) [1.8.9.jar:?]
at aya.a(SourceFile:238) [1.8.9.jar:?]
at axu.a(SourceFile:350) [1.8.9.jar:?]
at aya.a(SourceFile:495) [1.8.9.jar:?]
at axu.k(SourceFile:413) [1.8.9.jar:?]
at axu.p(SourceFile:390) [1.8.9.jar:?]
at ave.s(SourceFile:1498) [1.8.9.jar:?]
at ave.av(SourceFile:889) [1.8.9.jar:?]
at ave.a(SourceFile:325) [1.8.9.jar:?]
at net.minecraft.client.main.Main.main(SourceFile:124) [1.8.9.jar:?]
[22:34] [Server thread/INFO]: Starting integrated minecraft server version 1.8.9
[22:34] [Server thread/INFO]: Generating keypair
[22:34] [Server thread/INFO]: Preparing start region for level 0
[22:35] [Server thread/INFO]: Changing view distance to 8, from 10
[22:35] [Server thread/INFO]: Cheetah0307[local:E] logged in with entity id 332 at (1528.1551990434768, 90.30385776037632, 1281.0520900506272)
[22:35] [Server thread/INFO]: Cheetah0307 joined the game

PLEASE HELP!