Main Series:
Season 1: Indigo League
Film: Pokemon the First Movie - Mewtwo Strikes Back (~Episode 67)
Season 2: Aventures on the Orange Islands
Film: Pokemon the Movie 2000 - The Power of One (~Episode 107)
Season 3: The Jhoto Journeys
Film: Pokemon 3: The Movie - Spell Of the Unown (~Episode 161)
Season 4: Johto League Champions
Film: Pokemon 4Ever - Celebi: Voice of the Forest (~Episode 213)
Season 5: Master Quest
Film: Pokemon Heroes (~Episode 266)
Season 6: Advanced
Film: Jirachi: Wish Maker (~Episode 331)
Season 7: Advanced Challenge
Film: Destiny Deoxys (~Episode 387)
Season 8: Advanced Battle
Film: Lucario and the Mystery of Mew (Mew and the Aura Hero: Lucario) (~AG 082 and AG 108)
Season 9: Battle frontier
Film: Pokemon Ranger and the Temple of the Sea (Pokemon Ranger and the Prince of the Sea: Manphy) (~AG 148 and the end of the series at AG192)
Season 10: Diamond and Pearl
Film: The Rise of Darkrai (Dialga VS Palkia VS Darkrai) (~DP 038 and DP 055)
Season 11: DP: Battle Dimension
Film: Giratina and the Sky Warrior (Giratina and the Bouquet of the Frozen Sky: Shaymin) (~DP 085 and DP 100)
Season 12: DP: Galactic Battles
Film: Arceus and the Jewel of Life (Arceus: To Conquering Space-Time) (~DP 132 and DP 163)
Season 13: DP: Sinnoh League Victors
Film: Zoroark—Master of Illusions (Phantom Ruler: Zoroark) (~DP 171 and the end of the series at 192)
Season 14: Black & White
Film:
White—Victini and Zekrom (Victini and the Black Hero: Zekrom)
Black—Victini and Reshiram (Victini and the White Hero: Reshiram)
(~Between BW 024 and BW 077)
Season 15: BW: Rival Destinies
Film: Kyurem vs. the Sword of Justice (Kyurem vs. the Sacred Swordsman: Keldeo) (~BW 077 and 116)
Season 16: BW: Adventures in Unova and BW: Adventures in Unova and Beyond
Film: Genesect and the Legend Awakened (ExtremeSpeed Genesect: Mewtwo Awakens) (~BW 116 and the end of the series at BW 144)
Season 17: XY
Film: Diancie and the Cocoon of Destruction (~XY 038 and XY 052)
Season 18: XY: Kalos Quest
Film: Hoopa and the Clash of Ages (The Archdjinni of the Rings: Hoopa) (~XY 067 and XY 100)
Season 19: XYZ
Film: Volcanion and the Mechanical Marvel (Volcanion and the Exquisite Magearna) (~XY 110 and XY 126)
Season 20: Sun and Moon
Film: I Choose You (Does not matter, it isn't related to the main story, only another universe if Ash decided to follow Ho-Oh
Season 21: Ultra Adventures
Film: Everyone's Story (Again does not matter, filler film)
Here are two lists, I based my answers off of those, specifically the movies with way more detail:
https://anime.stackexchange.com/que...emon-movies-occur-chronologically-to-the-plot
https://www.alltimelines.com/pokemon/2/
List of episodes: (Season 1-13)
https://en.wikipedia.org/wiki/List_of_Pokémon_episodes_(seasons_1–13)
List of episodes (Season 14 - Current)
https://en.wikipedia.org/wiki/List_of_Pokémon_episodes_(seasons_14–current)