Changing citation reference systems I am writing a research paper for the first time and I submitted my paper to a journal, in which the references in my paper were addressed in parentheses, as follows: 

".....be preferentially located in the nuclear interior (Saccone et al. 2002; Cremer et al. 2015), consistent with a less compact organization and an enrichment of long-range chromosomal contacts with other active TADs and potentially multi-TAD hubs (Yaffe and Tanay, 2011; Olivares-Chauvet et al. 2016)."

The journal rejected it, and I submitted it to another journal which wants the references as follows: 

".....be preferentially located in the nuclear interior [1-2], consistent with a less compact organization and an enrichment of long-range chromosomal contacts with other active TADs and potentially multi-TAD hubs [3-4]."


Saccone et al. 2002
Cremer et al. 2015
Yaffe and Tanay, 2011
Olivares-Chauvet et al. 2016


In the current format I have, all my references have the name and year in the parentheses and the full references at the end of the manuscript. The new journal wants it as numbers in order of occurrence in the manuscript. 

Does anyone know any easy way to change the formats, without buying any software? If this question is out of scope of this forum, is there an appropriate one where I should ask?

Any help would be hugely appreciated, thank you so much! 

Cheers,
The easiest way to switch from one reference style to another is to manage the references using softwares. You may use Mendeley or Zotero, which are free reference management softwares. EndNote is another option but you need to purchase it. A free version of EndNote with basic functionality is also available.