Translation:I swam from France to England one time.
"Swam" and "swum" are not interchangeable. "Swam" is the past for "to swim" and "swum" is the past participle. In English, two tenses are used to describe events that happened in the past - the simple past (https://en.wikipedia.org/wiki/Simple_past) and the present perfect (https://en.wikipedia.org/wiki/Present_perfect). You use "swam" for the simple past tense in English. You use "have swum" for the present perfect tense. The present perfect in English is formed with the past participle ("swum") and the present tense of "to have". you cannot use "swum" by itself.
In the example here, the expression "one time" indicates that the English simple past should be used because we are talking about a single event. So, "I swam from France to England one time" is correct in English. You could also use the simple past tense for habitual actions in the past that have a defined time frame. For example, "Every morning that summer, I swam a couple of miles in the English channel".
You would use the present perfect (e.g., "have swum") "chiefly for completed past actions or events, when it is understood that it is the present result of the events that is focused upon, rather than the moment of completion. No particular past time frame is specified for the action/event" (see above link on "present perfect"). For example, one could say "I have swum from France to England before". "Before" does not indicate a specific time frame. In fact, one could say "I have swum from France to England before, and I'm thinking of doing it again." One could also say "I have just swum from France to England". "If the frame of reference extends to the present time, the present perfect is used" (https://en.wikipedia.org/wiki/Uses_of_English_verb_forms#Present_perfect).
You might hear "once" more commonly than "one time", especially at the end of the sentence, but "one time" is used in English.
Putting "one time" at the beginning might sound more natural for some people (e.g. "One time, I swam from France to England")
I perhaps should point out an American movie that made good use of the phrase "one time" - American Pie (https://www.youtube.com/watch?v=MH619vxtNdo). ("This one time at band camp" is now a pop culture reference.)